1. Field of the Invention
The invention concerns cosmetic compositions, especially color cosmetics such as facial foundations, effective at counteracting the signs of aging including fine lines and wrinkles while remaining non-irritating to the treated skin.
2. The Related Art
Emollients such as fats, phospholipids and sterols have in the past been used to soften wrinkled or dry skin. These emollients are only partially effective as a remedy for skin in poor condition.
The use of .alpha.-hydroxy carboxylic acids for enhancing the quality of human skin has been known for some time. There is no doubt that .alpha.-hydroxy carboxylic acids are therapeutically effective much beyond the common emollients.
U.S. Pat. No. 4,424,234 (Alderson et al.) discloses skin treatment compositions incorporating .alpha.-hydroxycaproic acid and .alpha.-hydroxycaprylic acid or mixtures thereof in compositions that have a pH value of less than 7, usually from 2 to 4. Yu and Van Scott have patented widely in this area. For instance, U.S. Pat. No. 4,105,782 reports amines or ammonium salts of .alpha.-hydroxy carboxylic acids in the treatment of acne or dandruff. In U.S. Pat. No. 4,105,783 and U.S. Pat. No. 4,197,316, these compounds are suggested for the treatment of dry skin. U.S. Pat. No. 4,234,599 discloses the use of .alpha.-hydroxy carboxylic acids, their esters or amine salts in the treatment of keratoses. More recently, U.S. Pat. No. 5,091,171 focused attention on these compounds as being effective against age spots, wrinkles and aging related skin changes.
While .alpha.-hydroxy carboxylic acids hold much therapeutic promise, these materials have been found to irritate human skin on repeated topical applications. The irritation may range from a sensation of tingling, itching and burning to clinical signs of redness and peeling. Causes for such irritation have been linked to the lowering of pH in the stratum corneum of human skin. Low pH has been suggested as provoking disturbances in intercorneocyte bondings resulting in adverse skin reactions, specially in some individuals with sensitive skin.
Accordingly, it is an object of the present invention to provide a composition including .alpha.-hydroxy carboxylic acids with a carrier formulation that avoids irritation including the sensation of stinging, itching and burning as well as any clinical signs of redness and peeling.
It is another object of the present invention to provide a cosmetic composition that is functionally effective against age spots, wrinkling and related aging changes.
Still another object of the present invention is to provide a cosmetic composition, especially a color cosmetic such as a facial foundation, which exhibits a smooth silky, slippery texture.
These and other objects of the present invention will become more readily apparent from consideration of the following summary, detailed description and examples which follow.